The specific objective of the proposed research project is to measure and analyze the results of a longitudinal experimental study that will have been in progress for nearly three years when the proposed project begins. The overall objective of the longitudinal study is to discover the degree to which the most malnourished and otherwise deprived three-year- old children from the poorest sectors of the large urban area of Cali, Columbia can be helped to achieve the levels of health, cognitive development and social competence found among upper class children of the same age by six years of age. Since 1970, groups of preschool age children have been receiving differential treatments to test the effectiveness of one, two or three years of continuous intensive nutritional supplementation, health care, intellectual demand, and social interaction. These groups of children are to be compared simultaneously with groups of children receiving nutritional supplementation and health care for similar periods of time, untreated upper class children and children from the same economically depressed sectors, on several biomedical and behavioral measures of competence.